1. Field of the Invention
The present invention relates to a white balance adjusting device for use in a camera which picks up an image of a field and then creates a video signal representing the field.
2. Description of the Related Art
Generally, in a video camera, it is necessary to adjust a white balance in a video signal according to kinds of illumination light to be used in photographing.
This is because, in view of the fact that a color video camera has no adaptability with respect to colors unlike the human eyes, the white balance must be adjusted so that the black and white colors of the field can be observed as the same black and white colors in a monitor image receiving device as well. Thus, in order that the color separation components of a video signal obtained from an image pickup device can be uniform, the amplitude gains of the color separation components are to be adjusted (which is generally referred to as a white balance adjustment) according to the color temperatures of the illumination light used.
In a conventional white balance adjusting device of this type, there is provided a color temperature sensor in a camera and the white balance can be automatically adjusted in accordance with the color temperatures that have been sensed by the color temperature sensor.
In the above-mentioned conventional white balance adjusting device for use in a camera, when taking a picture in fine weather conditions in the normal light, if the blue sky occupies a larger share with respect to the angle of field, the color temperature detects a color temperature higher than that of a daylight in the fine weather conditions. That is, a color temperature which corresponds to a temperature in the shade is detected, in spite of the blue sky. Therefore, in this case, if the white balance is adjusted in accordance with the detection output of the color temperature sensor, then the adjusted colors go toward a yellow color from the color balance that they originally ought to be. Thus is, a proper white balance adjustment cannot be performed.